1. Field of Invention
This invention relates to medical instruments. More particularly, this invention relates to hemostasis valves, or the like which may be used in a wide variety of medical procedures.
2. Prior Art
The introduction of catheters into blood vessels for a variety of purposes such as coronary angiography has been known for many years. Several techniques for introducing these catheters are available. One such technique is the cut-down method. Another is the Seldinger technique. This technique involves surgically opening a vein or artery with a needle, inserting a guidewire into the vessel through the lumen of the needle, withdrawing the needle, inserting over the guidewire a dilator located inside an associated hemostasis valve and sheath, removing the dilator and inserting a catheter through the hemostasis valve and sheath and into the blood vessel.
A wide variety of hemostasis valves are known in the prior art. However, when a guidewire is inserted through most hemostasis valves, because the guidewire is so small relative to the catheters which may also be employed, it is difficult for the valve to seal against the backward pressure of blood, while at the same time permitting easy insertion of much larger diameter catheters. This problem is particularly acute with procedures involving arterial invasion where there is a high reverse pressure of blood. In these arterial procedures, blood can often squirt out when the guidewire is introduced through the hemostasis valve. Excessive blood leakage is viewed by many as extremely dangerous. Most prior art hemostasis valves are designed for use with a particular size of catheter. Because adequate sealing around the catheter walls cannot be obtained for catheters having a range of diameters, it has often not been possible in the past to employ a single hemostasis valve with catheters of widely varying diameters.
In U.S. Pat. No. 4,000,739, the hole (26), is described as being similar in size to the body of the cannula (46) which is introduced into the body. Since, as shown in FIG. 3, the guidewire is several orders of magnitude smaller than the cannula body, any guidewire inserted through the valve is not sealed by the disc (22). While some sealing does occur with the disc (24), the sealing is often not sufficient to stop a reverse flow of blood when only the guidewire is present. Also, because the discs (22) and (24) function independently, it is often possible for the guidewire to move off center of the disc (24), thereby causing a further leakage of blood.
U.S. Pat. No. 4,436,519 discloses a combination of a donut-shaped gasket and a second cup-shaped seal. The device described in the '519 patent is deficient because its donut-shaped gasket can only accept catheters having a relatively limited range of diameters. Moreover, this device is particularly susceptible to leakage when only the guidewire is in place.
The devices described in U.S. Pat. No. 4,673,393, particularly in FIGS. 4 and 5 do not force the centering of the guidewire. Instead, the guidewire may move off-center of the slits and thereby increase the likelihood of a backward flow of blood. A similar problem is seen with the plug described in U.S. Pat. No. 4,610,655 in FIGS. 4 and 5(a).
U.S. Pat. No. 4,655,752 discloses a surgical cannula which again suffers from the deficiency that the first sealing member (79) will not center a guidewire. Moreover, this cannula, like other prior art cannulas, suffers from a lack of universality and from poor sealing. While two seals are employed, the second seal may only be used with catheters having a limited range of diameters and will provide little or no sealing around a guidewire.
U.S. Pat. No. 4,634,432 describes an introducer sheath assembly which contains a single disc (52) having a single slit therein. This disc will permit movement of a guidewire to an off-center position which in turn allows leakage of blood.
U.S. Pat. No. 4,424,833 discloses a gasket assembly in which the opening (48) is large enough to permit a great deal of movement of a guidewire which in turn will permit increased leakage of blood.
U.S. Pat. No. 4,798,594 discloses a hemostasis valve comprised of a plurality of helical slits. Because a pilot or other guiding hole is not present, the guidewire introduced into this valve can readily be skewed off-center, thereby permitting the reverse flow of blood. In a similar fashion, U.S. Pat. No. 4,626,245 describes a valve body containing two Y-shaped slits which are offset one from the other. This offset alignment permits a guidewire inserted into the cannula to move into an off-center position and thereby encourages the reverse leakage of blood.
Another problem shown by many prior art hemostasis cannulas is that the surgeon must be able to "feel" the catheter as it is inserted through the gaskets or other sealing members of the hemostasis unit and ultimately into a blood vessel. If insertion of the catheter through the hemostasis valve is inhibited by friction, the cannula unit may be rejected by surgeons as being difficult to use during catheter insertion. Concommitantly, the use of hemostasis valves which exert undue pressure on the side walls of inserted catheters may lead to excessive hemodynamic dampening of the catheter. In other words, excessive pressure on the exterior side walls of a catheter may cause a narrowing of the catheters diameter thereby altering measurement parameters taken within the catheter.
German Patent No. 3,042,229 purports to describe a hemostasis valve which may be used with catheters having a variety of diameters. However, the sealing means of the device described in the '729 patent is formed from two separate pieces thereby increasing the difficulties of manufacture and the likelihood that one of the seals may become dislodged particularly when large diameter catheters are employed.
Among the prior art hemostasis plug valves or cannulas which offer improvements over prior art devices is included commonly assigned U.S. Pat. No. 4,909,798.
Thus, it is important, in providing a sealing mechanism for a hemostasis valve unit, that the mechanism:
1. Be universal, i.e., useful with both guidewires and with catheters having a wide range of diameters;
2. Provide for relatively easy insertion of all diameters of catheters; and
3. Be free from excessive restriction which would cause hemodynamic dampening.
Accordingly, it is an object of this invention to prepare a hemostasis valve which can effectively seal around both guidewires and cannulas of varying diameters.
It is another object of this invention to prepare a hemostasis valve which is held in the desired position and is not readily displaced by the action of a cannula inserted therethrough.
It is a further object of this invention to prepare a hemostasis valve which will effectively center guidewires to ensure that they do not move to an off-center position, thereby permitting leakage of blood.
It is yet another object of this invention to construct a hemostasis cannula unit which will permit the use of catheters having a wide variety of diameters, while at the same time allowing insertion of any of these catheters without undue pressure/friction thereby providing good surgical "feel" for all diameters of catheters and reduced hemodynamic pressure dampening.
These and other objectives are obtained by utilizing the device described hereafter.